Is Wisconsin loss beginning of the end for Donald Trump?

You know the Republican presidential race really has taken a strange turn when a man resembling a ‘50s throwback and widely loathed by his colleagues emerges as the darling of the party establishment.

Ted Cruz - never previously an object of widespread affection - claimed his place in the spotlight and Republican insiders’ hearts with an emphatic win in Tuesday's Wisconsin primary that sets his party on course for a contested convention in Cleveland in July.

Watch | Ted Cruz's controversial quotes

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By winning this major mid-western state - and with a resounding margin - the abrasive Texas senator effectively became the sole weapon with which the party establishment can halt the march of Donald Trump.

Mr Trump, seemingly impregnable until a recent catalogue of missteps rendered him suddenly vulnerable, acknowledged as much in a blunt missive that was striking in its vituperation even by his standards.

“Donald J Trump withstood the onslaught of the establishment yet again,” read the statement issued by his campaign headquarters.

“Lyin’ Ted Cruz had the governor of Wisconsin, many conservative talk radio show hosts, and the entire party apparatus behind him. [He] is worse than a puppet - he’s a Trojan horse being used by the party bosses attempting to steal the nomination from Mr Trump.”

Fuelling the anger behind such fighting talk was Mr Cruz’s margin of victory - sufficiently large to ensure that he won the lion’s share of Wisconsin’s 42 delegates under the state Republican party’s winner-takes-most system.

Donald Trump had some angry words for the Republican establishment after his defeat in Wisconsin.Credit:
AP

That makes Mr Trump’s task of reaching the magic figure of 1,327 delegates needed to secure the nomination much tougher - and opens the door to a contested convention in which GOP grandees will try to exploit any shortfall to wrest the prize away from him.

To tie up the nomination before the convention, Mr Trump must now win a much higher proportion of the delegates - 57 per cent - in the remaining contests than the 48 per cent he managed in the previous primaries while seemingly all-conquering and cutting a swathe through the Republican field.

"Lyin’ Ted Cruz had the governor of Wisconsin, many conservative talk radio show hosts, and the entire party apparatus behind him. [He] is worse than a puppet - he’s a Trojan horse being used by the party bosses attempting to steal the nomination from Mr Trump"

The primary cavalcade now heads to Maryland, Connecticut and - of all places - New York, the brash property tycoon’s backyard, where the fight is only bound to get uglier.

Watch | US Election 2016 explained

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From the Big Apple, Mr Trump is almost certain to throw Mr Cruz’s past disparaging comments about “New York values” back at him - exploiting deep-seated emotions and memories about the city’s suffering in the wake of the 9/11 terrorist attacks.

Addressing his supporters in Milwaukee on Tuesday night, Mr Cruz called his victory in Wisconsin “a turning point”, adding: “I’m more convinced than ever that our campaign is going to earn the 1,237 delegates needed to win, either before Cleveland or at the convention in Cleveland.”

To that, Mr Trump may have been thinking: “Don’t speak too soon: wait till you see what I have in store for you in New York.”